Bob - some old cures are NOT silly.
From Wikipedia
A goitre or goiter (Latin gutteria, struma), is a swelling in the thyroid gland,[1] which can lead to a swelling of the neck or larynx (voice box). Goitre is a term that refers to an enlargement of the thyroid and can be associated with a thyroid gland that is functioning properly or not.

Worldwide, over 90% cases of goitre are caused by iodine deficiency.

Your father clearly knew his stuff...

Quack!
GtD.